@misc{EfimovaHubrigSchmidt, author = {Efimova, Anastasia and Hubrig, Grit and Schmidt, Peer}, title = {Thermal stability and crystallization behavior of imidazolium halide ionic liquids}, series = {Thermochimica Acta}, volume = {Vol. 573}, journal = {Thermochimica Acta}, issn = {0040-6031}, doi = {10.1016/j.tca.2013.09.023}, pages = {162 -- 169}, abstract = {The 1-butyl-3-methylimidazolium halide ionic liquids are stable up to temperatures of 246(1) °C ([BMIm]Cl), 260(1) °C ([BMIm]Br), and 238(1) °C ([BMIm]I). The thermal decomposition proceeds in thermogravimetric measurements with a total mass loss of 100\%. Using evolved gas analysis (EGA) a complete degradation of [BMIm]X ionic liquids under formation of characteristic fragments CH3+, NHn+, C4Hn+, and CH3X+ (X = Cl, Br, I) has been observed. [BMIm]Cl shows enantiotropic polymorphism with a phase transition temperature at 30(1) °C, and melts at 74(1) °C (ΔHfus = 18 ± 0.5 kJ mol-1). Spontaneous e-crystallization and reversible phase transition have been found for cooling of the substance.[BMIm]Br melts at 78(1) °C (ΔHfus = 29 ± 0.5 kJ mol-1). The re-crystallization fails and thus a glassy solid is formed. The glass transition temperature is about -65 °C, the cold crystallization occurs between -30 and -20 °C. The application of both homogeneous and heterogeneous nucleation agents does not interfere the glassy state. [BMIm]I undergo solidification without crystallization. The melting effect for the amorphous substance arise at -70(5) °C with ΔHfus = 0.4 ± 0.2 kJ mol-1.}, language = {en} } @misc{EfimovaPinnauMischkeetal., author = {Efimova, Anastasia and Pinnau, Sebastian and Mischke, Matthias and Breitkopf, Cornelia and Ruck, Michael and Schmidt, Peer}, title = {Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling}, series = {Thermochimica Acta}, volume = {45}, journal = {Thermochimica Acta}, number = {575}, issn = {0040-6031}, doi = {10.1016/j.tca.2013.11.011}, pages = {276 -- 278}, abstract = {Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 ◦C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO3)2·6H2O, Mn(NO3)2·4H2O, and KNO3 with the melting temperature range 18-21 ◦C and the enthalpy of fusion of about 110 kJ kg-1. Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation.}, language = {en} } @misc{EfimovaPfuetznerSchmidt, author = {Efimova, Anastasia and Pf{\"u}tzner, Linda and Schmidt, Peer}, title = {Thermal Stability and Decomposition Mechanism of 1-Ethyl-3-Methylimidazolium Halides}, series = {Thermochimica Acta}, volume = {604}, journal = {Thermochimica Acta}, doi = {10.1016/j.tca.2015.02.001}, pages = {129 -- 136}, abstract = {The thermochemical behavior of 1-ethyl-3-methylimidazolium [EMIm] halides (Cl, Br and I) has been investigated for their crystalline and liquid states in the temperature range from -90 °C to 600 °C using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The temperatures and enthalpies of phase transitions have been determined: Tfus = 86(1) °C, ΔHfus = 14.2(0.7) kJ mol-1 ([EMIm]Cl); Tfus = 67(1) °C, ΔHfus = 19.3(0.7) kJ mol-1 ([EMIm]Br); and Tfus = 74(1) °C, ΔHfus = 16.9(0.6) kJ mol-1 ([EMIm]I). The decomposition temperatures, determined by onset of DTG at 1 K min-1 are 233(5) °C ([EMIm]Cl), 246(5) °C ([EMIm]Br), and 249(5) °C ([EMIm]I). The maximum operation temperature (MOT) has been estimated based on dynamic TGA for an operation time of 24 h: 132 °C ([EMIm]Cl), 149 °C ([EMIm]Br), 139 °C ([EMIm]I) and 8000 h: 76 °C ([EMIm]Cl), 90 °C ([EMIm]Br), 77 °C ([EMIm]I). The decomposition products of the investigated ionic liquids (ILs) after heating experiments were identified by means of TGA complemented with mass spectrometry (MS), for establishment of the mechanism of thermal decomposition of the ILs. Complete degradation of [EMIm]X ionic liquids occurs under formation of characteristic molecule fragments CH3+, NH+, and X+, CH3X+, C2H5X+ (X = Cl, Br, I).}, language = {en} } @misc{GrohBreternitzAhmedetal., author = {Groh, Matthias F. and Breternitz, Joachim and Ahmed, Ejaz and Isaeva, Anna and Efimova, Anastasia and Schmidt, Peer and Ruck, Michael}, title = {Ionothermal Synthesis, Structure, and Bonding of the Catena-Heteropolycation 1∞[Sb2Se2]+}, series = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie}, volume = {641}, journal = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie}, number = {2}, issn = {1521-3749}, doi = {10.1002/zaac.201400543}, pages = {388 -- 393}, abstract = {The reaction of antimony and selenium in the Lewis-acidic ionic liquid 1-butyl-3-methyl-imidazolium tetrachloridoaluminate, [BMIm]Cl·4.7AlCl3, yielded dark-red crystals of [Sb2Se2]AlCl4. The formation starts above 160 °C; at about 190 °C, irreversible decomposition takes place. The compound crystallizes in the triclinic space group Pequation image with a = 919.39(2) pm, b = 1137.92(3) pm, c = 1152.30(3) pm, α = 68.047(1)°, β = 78.115(1)°, γ = 72.530(1)°, and Z = 4. The structure is similar to that of [Sb2Te2]AlCl4 but has only half the number of crystallographically independent atoms. Polycationic chains 1∞[Sb2Se2]+ form a pseudo-hexagonal arrangement along [01-1], which is interlaced by tetrahedral AlCl4- groups. The catena-heteropolycation 1∞[Sb2Se2]+ is a sequence of three different four-membered [Sb2Se2] rings. The chemical bonding scheme, established from the topological analysis of the real-space bonding indicator ELI-D, includes significantly polar covalent bonding in four-member rings within the polycation. The rings are connected into an infinite chain by homonuclear non-polar Sb-Sb bonds and highly polar Sb-Se bonds. Half of the selenium atoms are three-bonded.}, language = {en} } @misc{PfisterSchaeferOttetal., author = {Pfister, Daniela and Sch{\"a}fer, Konrad and Ott, Claudia and Gerke, Birgit and P{\"o}ttgen, Rainer and Janka, Oliver and Baumgartner, Maximilian and Efimova, Anastasia and Hohmann, Andrea and Schmidt, Peer and Venkatachalam, Sabarinathan and W{\"u}llen, Leo van and Sch{\"u}rmann, Ulrich and Kienle, Lorenz and Duppel, Viola and Parzinger, Eric and Miller, Bastian and Becker, Jonathan and Holleitner, Alexander and Weihrich, Richard and Nilges, Tom}, title = {Inorganic double helices in semiconducting SnIP}, series = {Advanced Materials}, volume = {28}, journal = {Advanced Materials}, number = {44}, issn = {1521-4095}, doi = {10.1002/adma.201603135}, pages = {9783 -- 9791}, abstract = {SnIP is the first atomic-scale double helical semiconductor featuring a 1.86 eV bandgap, high structural and mechanical flexibility, and reasonable thermal stability up to 600 K. It is accessible on a gram scale and consists of a racemic mixture of right- and left-handed double helices composed by [SnI] and [P] helices. SnIP nanorods <20 nm in diameter can be accessed mechanically and chemically within minutes.}, language = {en} } @misc{EfimovaHubrigPfuetzneretal., author = {Efimova, Anastasia and Hubrig, Grit and Pf{\"u}tzner, Linda and Schmidt, Peer}, title = {Thermal Stability of Alkyl-Imidazolium-Ionic Liquids}, series = {Zeitschrift f{\"u}r Anorganische und Allgemeine Chemie}, volume = {640}, journal = {Zeitschrift f{\"u}r Anorganische und Allgemeine Chemie}, number = {11}, issn = {1521-3749}, doi = {10.1002/zaac.201490026}, pages = {2391}, abstract = {The thermochemical behavior of two groups of ionic liquids (ILs), 1-ethyl-3-methylimidazolium [EtMeIm] and 1-butyl-3-methylimidazolium [BuMeIm] halides (Cl, Br and I) was investigated for their crystalline and liquid states in the temperature range from -100 °C to 600 °C using DSC and thermogravimetric analysis (TGA). Some investigated ILs exhibit significant subcooling effect and the glass state formation [1]. The decomposition mechanism has been identified by means of TGA with coupled mass spectrometry (MS). All investigated ILs decompose with a total mass loss of about 100 \% in the temperature range of Tonset from 230 to 290 °C (Fig. 1). By complete degradation of IL, dominant fragments CnH2n+1+, CnH2n+, CnHn+, NHn+, and the respective alkyl halides (X = Cl, Br, I) are formed.}, language = {en} } @techreport{PinnauEfimovaSchmidt, author = {Pinnau, Sebastian and Efimova, Anastasia and Schmidt, Peer}, title = {Identifikation technischer Salze als Latentspeichermaterialien im Temperaturbereich von 4 bis 15 °C und deren Verkapselung: Abschlussbericht}, address = {Dresden}, doi = {10.2314/GBV:786966173}, pages = {92}, abstract = {Der Einsatz von thermischen Speichern erlaubt eine bessere Lastanpassung von Erzeugeranlagen zur Geb{\"a}udeklimatisierung sowie eine Optimierung des Betriebsregimes unter energetischen Gesichtspunkten. F{\"u}r solche Anwendungsf{\"a}lle k{\"o}nnen Latentw{\"a}rmespeicher zum Einsatz kommen, bei denen {\"u}blicherweise der Schmelz- und Erstarrungsvorgang sogenannter Phasenwechselmaterialien (Phase Change Materials, PCM) ausgenutzt wird. F{\"u}r die Anwendungstemperaturbereiche der Klimatisierung von etwa 4 °C bis 15 °C und f{\"u}r die K{\"u}hlung bis etwa 25 °C ist die Auswahl an Reinstoffen mit einer passenden Schmelztemperatur sehr begrenzt. Durch die Bildung von eutektischen Gemischen aus zwei oder mehr Komponenten - die {\"a}hnlich wie Reinstoffe einen scharfen Schmelzpunkt aufweisen - kann die Bandbreite an potentiellen PCM's f{\"u}r diesen Temperaturbereich vergr{\"o}ßert werden. F{\"u}r die genannten Temperaturbereiche werden vorzugsweise anorganische Salzhydrate als potentielle Speichermedien betrachtet, da diese gegen{\"u}ber organischen Substanzen h{\"a}ufig gr{\"o}ßere Schmelzenthalpien und geringere Kosten aufweisen.}, language = {de} } @misc{EfimovaVargaMatuscheketal., author = {Efimova, Anastasia and Varga, Janos and Matuschek, Georg and Saraji-Bozorgzad, Mohammad R. and Denner, Thomas and Zimmermann, Ralf and Schmidt, Peer}, title = {Thermal Resilience of Imidazolium-Based Ionic Liquids—Studies on Short- and Long-Term Thermal Stability and Decomposition Mechanism of 1-Alkyl-3-methylimidazolium Halides by Thermal Analysis and Single-Photon Ionization Time-of-Flight Mass Spectrometry}, series = {Journal of Physical Chemistry B}, volume = {122}, journal = {Journal of Physical Chemistry B}, number = {37}, doi = {10.1021/acs.jpcb.8b06416}, pages = {8738 -- 8749}, abstract = {Ionic liquids are often considered as green alternatives of volatile organic solvents. The thermal behavior of the ionic liquids is relevant for a number of emerging large-scale applications at elevated temperature. Knowledge about the degradation products is indispensable for treatment and recycling of the used ionic liquids. The objective of this paper was an investigation of the short- and long-term stability of several 1-alkyl-3-methylimidazolium halides, determination of the degradation products, and the elucidation of their decomposition patterns and structure-stability relations. Short-term stability and mechanism of thermal degradation were investigated by a self-developed, innovative thermal analysis single-photon ionization time-of-flight mass spectrometry device with Skimmer coupling. The applied technology provides real-time monitoring of the forming species and allows tracing their change during the course of the decomposition. Therein, the almost fragment-free soft ionization with vacuum ultraviolet photons plays a crucial role. We have detected unfragmented molecules whose formation was only assumed by electron ionization. Nevertheless, the main decomposition products of the selected ionic liquids were alkyl imidazoles, alkenes, alkyl halides, and hydrogen halides. From the decomposition products, we have deduced the fragmentation patterns and discussed their interrelation with the length of the alkyl chain and the type of the halide anion. Our results did not suggest the evaporation of the investigated ionic liquids prior to their decomposition under atmospheric conditions. Long-term thermal stability and applicability were determined based on thermogravimetric analysis evaluated with a kinetic model. Thus, the time-dependent maximum operation temperature (MOT) for the respective ionic liquids has been calculated. As a rule, the short-term stability overestimates the long-term decomposition temperatures; the calculated MOT are significantly lower (at least 100 K) than the standardly obtained decomposition temperatures.}, language = {en} } @misc{KniesKaiserLeAnhetal., author = {Knies, Maximilian and Kaiser, Martin and L{\^e} Anh, Mai and Efimova, Anastasia and Doert, Thomas and Ruck, Michael}, title = {Low-Temperature Ordering in the Cluster Compound (Bi₈)Tl[AlCl₄]₃}, series = {Inorganics}, volume = {7}, journal = {Inorganics}, number = {4}, doi = {10.3390/inorganics7040045}, pages = {1 -- 9}, abstract = {The reaction of Bi, BiCl₃, and TlCl in the ionic liquid [BMIm]Cl·4AlCl₃ (BMIm = 1-n-butyl-3-methylimidazolium) at 180 °C yielded air-sensitive black crystals of (Bi₈)Tl[AlCl₄]₃. X-ray diffraction on single crystals at room temperature revealed a structure containing [Tl(AlCl₄)₃]∞12- strands separated by isolated Bi₈²⁺ square antiprisms. The thallium(I) ion is coordinated by twelve Cl⁻ ions of six [AlCl₄]⁻ groups, resulting in a chain of face-sharing [TlCl₁₂]¹¹⁻ icosahedra. The Bi₈²⁺ polycation is disordered, simulating a threefold axis through its center and overall hexagonal symmetry (space group P6₃/m). Slowly cooling the crystals to 170 K resulted in increased order in the Bi₈ cluster orientations. An ordered structure model in a supercell with a' = 2a, b' = 2b, c' = 3c and the space group P6₅ was refined. The structure resembles a hexagonal perovskite, with complex groups in place of simple ions.}, language = {en} } @misc{MeissnerEfimovaSchmidt, author = {Meißner, Andr{\´e} and Efimova, Anastasia and Schmidt, Peer}, title = {Impacts of TGA furnace parameters for prediction of long-term thermal stability of ionic liquids}, series = {Thermochimica Acta}, volume = {704}, journal = {Thermochimica Acta}, doi = {10.1016/j.tca.2021.178917}, pages = {178917-1 -- 178917-7}, abstract = {The concept of maximum operation temperature is established for the prediction of the time dependent thermal stability of ionic liquids based on kinetic evaluation of thermogravimetric analysis. The influence of the furnace control parameters on the maximum operation temperature (MOT) is shown using the example of 1-methyl-3-propylimidazolium iodide ([C3C1im]I) with respect to three different parameter sets of a programmed proportional integral derivative (PID) controller of the TGA. Kinetics of thermal decomposition of [C3C1im]I have been investigated with the implementation of an improved kinetic model. The activation energy obtained using the Kissinger-Akahira-Sunose equation showed variations apparently due to the decomposition degree. The model compound is decomposed by a one-step kinetics, which results from pseudo zero order relationship of the activation energy to the conversion rate. The activation energy, pre-exponential factor, and the activation energy are strongly dependent on the parameters of TGA furnace controller.}, language = {en} } @misc{IvshinMetlushkaZinnatullinetal., author = {Ivshin, Kamil and Metlushka, Kirill and Zinnatullin, Ruzal and Nikitina, Kristina and Pashagin, Alexander and Zakharychev, Dmitry V. and Efimova, Anastasia and Kiiamov, Airat and Latypov, Shamil and Kataeva, Olga}, title = {Competitive Hydrogen Bonding and Unprecedented Polymorphism in Selected Chiral Phosphorylated Thioureas}, series = {Crystal Growth Design}, volume = {21}, journal = {Crystal Growth Design}, number = {9}, issn = {1528-7505}, doi = {10.1021/acs.cgd.1c00758}, pages = {5460 -- 5471}, abstract = {New racemic and enantiopure N-phosphorylated thioureas bearing 1-phenylethyl or tetrahydronaphthalenyl fragments were synthesized. According to NMR data assisted by DFT calculations, the preferred conformation is stabilized by an intramolecular hydrogen bond. This form in solution is in equilibrium with dimeric N-H···S hydrogen-bonded associates, the population depending on the concentration. In the crystalline phase the low-energy conformation with an intramolecular H-bond is realized only in the racemic tetrahydronaphthalenyl derivative. In most crystals various types of intermolecular hydrogen bonding are observed, accompanied by the formation of infinite linear chains or helical structures. Due to the conformational lability of compounds and competitive intermolecular H-bonding, multiple polymorphic modifications are formed. Therefore, crystallization of enantiopure 1-phenylethyl derivatives from various solvents results in concomitant polymorphs at room temperature. One of them undergoes reversible two-step phase transitions from the high-symmetry I41 space group (Z′ = 1, no disorder) via the P41 space group (Z′ = 6) to the monoclinic P21 space group (Z′ = 16) accompanied by drastic concerted conformational changes. Notably, the optimization of the crystal packing is observed upon phase transitions with a gradual reduction of the void space in the unit cell from 4.5\% to 0.8\%. This is a rare case of several high-Z′ polymorphs for one compound, with chirality playing an important role.}, language = {en} } @misc{VinokurovaKnorrEfimovaetal., author = {Vinokurova, Ekaterina and Knorr, Monika and Efimova, Anastasia and Ovchinnikov, Alexander and Schmidt, Peer and B{\"u}chner, Bernd and Isaeva, Anna and Roslova, Maria}, title = {Microstructural evolution of layered K-doped RuCl3 during annealing traced by thermogravimetric analysis and 3D electron diffraction}, series = {Zeitschrift f{\"u}r Anorgische und Allgemeine Chemie}, volume = {649}, journal = {Zeitschrift f{\"u}r Anorgische und Allgemeine Chemie}, number = {19}, issn = {0044-2313}, doi = {10.1002/zaac.202300141}, pages = {1 -- 8}, abstract = {Nanoscale phase separation was induced in the K-doped RuCl3 van der Waals material by annealing, and studied with the goal to find a natural design strategy for the formation of two-dimensional architectures as an alternative to the costly and time-consuming experimental artificial growth methods. Phase conversion was traced by means of thermogravimetric analysis combined with mass spectrometry. The local crystal structure of co-existing K3Ru2Cl9 domains with the sizes of about 100 nm was solved by 3D electron diffraction.}, language = {en} } @techreport{SchmidtEfimova, author = {Schmidt, Peer and Efimova, Anastasia}, title = {Kristallisationsverhalten von Phasenwechselmaterialien als Latentw{\"a}rmespeicher (KristallLaW): Abschlussbericht}, publisher = {BTU Cottbus - Senftenberg, Fachgebiet Anorganische Chemie}, address = {Senftenberg}, doi = {10.2314/GBV:884496287}, pages = {44}, abstract = {Phasenwechselmaterialien (PCM) sind chemische Verbindungen oder deren Mischungen, die bei einer definierten Temperatur schmelzen bzw. erstarren. Der zyklische Einsatz von W{\"a}rmespeichern erm{\"o}glicht den Ausgleich von {\"U}berlasten f{\"u}r den Bedarf oder den „Abfall" von W{\"a}rme sowie die Vergleichm{\"a}ßigung von W{\"a}rmeprofilen. Bestehende anorganische Materialien weisen {\"u}berwiegend Einschr{\"a}nkungen bez{\"u}glich der Anforderungen an eine geringe Hysterese von Aufheizung und Abk{\"u}hlung auf. Das Maß der Unterk{\"u}hlung der Schmelze sowie ein zyklenstabiler W{\"a}rmeaustausch kann aber durch Zus{\"a}tze als Kristallisationshilfen (Keimbildner) gesteuert werden. Im vorliegenden Bericht werden die Keimbildung und Kristallisation von Phasenwechselmaterialien unter folgenden Gesichtspunkten diskutiert: Methoden der Thermischen Analyse zur Untersuchung der thermochemischen Eigenschaften von PCM, thermochemische Eigenschaften anorganischer Salze und Salzhydrate als PCM, dominierende Kristallstrukturen und Strukturmotive anorganischer Salze und Salzhydrate als PCM, dominierende Kristallstrukturen und Strukturmotive anorganischer Stoffe als homogener und heterogener Keimbildner, {\"A}nderung der thermochemischen Eigenschaften von PCM bei Zusatz von Keimbildnern, geeignete Konzentrationsbereiche von Keimbildnern, Homogenit{\"a}t/Segregation von Phasen.}, language = {de} } @misc{EhrlingSenkovskaEfimovaetal., author = {Ehrling, Sebastian and Senkovska, Irena and Efimova, Anastasia and Bon, Volodymyr and Abylgazina, Leila and Petkov, Petko and Evans, Jack D. and Attallah, Ahmed Gamal and Wharmby, Michael Thomas and Roslova, Maria and Huang, Zhehao and Tanaka, Hideki and Wagner, Andreas and Schmidt, Peer and Kaskel, Stefan}, title = {Temperature Driven Transformation of the Flexible Metal-Organic Framework DUT-8(Ni)}, series = {Chemistry - a European journal}, volume = {28}, journal = {Chemistry - a European journal}, number = {55}, issn = {1521-3765}, doi = {10.1002/chem.202201281}, pages = {1 -- 10}, abstract = {DUT-8(Ni) metal-organic framework belongs to the family of flexible pillared layer materials. The desolvated framework can be obtained in the open pore form (op) or in the closed pore form (cp), depending on the crystal size regime. In the present work, we report on the behaviour of desolvated DUT-8(Ni) at elevated temperatures. For both, op and cp variants, heating causes a structural transition, leading to an new, crystalline compound, containing two interpenetrated networks. The state of the framework before transition (op vs. cp) influences the transition temperature: the small particles of the op phase transform at significantly lower temperature in comparison to the macroparticles of the cp phase, transforming close to the decomposition temperature. The new compound, confined closed pore phase (ccp), was characterized by powder X-ray diffraction and spectroscopic techniques, such as IR, EXAFS, and positron annihilation lifetime spectroscopy (PALS). Thermal effects of structural cp to ccp transitions were studied using differential scanning calorimetry (DSC), showing an overall exothermic effect of the process, involving bond breaking and reformation. Theoretical calculations reveal the energetics, driving the observed temperature induced phase transition.}, language = {en} } @misc{KnorrIckerEfimovaetal., author = {Knorr, Monika and Icker, Maik and Efimova, Anastasia and Schmidt, Peer}, title = {Reactivity of Ionic Liquids: Studies on Thermal Decomposition Behavior of 1-Butyl-3-methylimidazolium Tetrafluoroborate}, series = {Thermochimica Acta}, volume = {Vol. 694}, journal = {Thermochimica Acta}, issn = {0040-6031}, doi = {10.1016/j.tca.2020.178786}, pages = {1 -- 11}, abstract = {The Ionic Liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C4C1im]BF4 serves as a commonly solvent in inorganic material synthesis and analytics. Nevertheless, its application is frequently associated with trial and error approaches. Thereupon, detailed knowledge on the thermal behavior is the key information for understanding the reactivity of [C4C1im]BF4. 1-butyl-3-methylimidazolium tetrafluoroborate behaves as a glass in the cold, its glass transition temperature being ϑg = -83 °C. During heating with 10 K·min-1 [C4C1im]BF4 appears to be stable above 350 °C with onset temperatures ϑonset, DSC = 375 °C, ϑonset, DTG = 422 °C, and ϑonset, TG = 437 °C. Thereby, thermal decomposition occurs in a single step reaction forming 1-methyl-1H-imidazole (CH3C3H3N2 or C4H6N2), but-1-ene (C4H8), fluoromethane (CH3F) and boron trifluoride (BF3) as main species, as determined by thermogravimetry coupled with mass spectrometry and FTIR spectroscopy. To be more specific in thermal behavior, the temperature and time dependent stability is evaluated here on the basis of the kinetic model of maximum operation temperature - MOT. Clearly, thermal stability rises with application time, thus being 193 °C for one hour, while reaching only 141 °C for one day, and 114 °C for one week. The incipient decomposition (≤ 1 \%) at the calculated time dependent maximum operation temperature finally is verified by optical analysis, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy.}, language = {en} } @misc{GaraiBonEfimovaetal., author = {Garai, Bikash and Bon, Volodymyr and Efimova, Anastasia and Gerlach, Martin and Senkovska, Irena and Kaskel, Stefan}, title = {Reversible switching between positive and negative thermal expansion in a metal-organic framework DUT-49}, series = {Journal of Materials Chemistry A}, volume = {39}, journal = {Journal of Materials Chemistry A}, number = {8}, issn = {2050-7496}, doi = {10.1039/D0TA06830F}, pages = {20420 -- 20428}, abstract = {Three-dimensional architectures constructed via coordination of organic ligands to metal ions (broadly termed metal-organic frameworks, MOFs), are highly interesting for many demanding applications such as gas adsorption, molecular separation, heterogeneous catalysis, molecular sensing, etc. Being constructed from heterogeneous components, such framework solids show characteristic features from both the individual components and framework-specific features. One such interesting physicochemical property is thermal expansion, which arises from thermal vibration from the organic linker and metal ions. Herein, we show a very unique example of thermal responsiveness for the DUT-49 framework, a MOF well-known for its distinctive negative gas adsorption (NGA) properties. In the guest-free form, the framework shows another counter-intuitive phenomenon of negative thermal expansion (NTE), i.e. the lattice size increases with decrease of temperature. However, in the solvated state, it shows both NTE and positive thermal expansion (i.e. lattice size decreases with lowering of temperature, PTE) based on a specific temperature range. When the solvent exists in the liquid form inside the MOF pore, it retains the pristine NTE nature of the bare framework. But freezing of the solvent inside the pores induces the strain, which causes a structural transformation through in-plane bending of the linker and this squeezes the framework by ∼10\% of the unit cell volume. This effect has been verified using 3 different solvents where the structural contraction occurs immediately at the freezing point of the individual solvent. Furthermore, studies on a series of DUT-49(M) frameworks with varying metals confirm the general applicability of this mechanism.}, language = {en} } @misc{SchmidtEfimova, author = {Schmidt, Peer and Efimova, Anastasia}, title = {Thermal Characterization of Ionic Liquids}, series = {OnSet : News, Facts and Professional Solutions for Thermal Analysis}, volume = {15}, journal = {OnSet : News, Facts and Professional Solutions for Thermal Analysis}, pages = {14 -- 17}, abstract = {Ionic liquids (ILs) are currently of high interest due to their high performance physicochemical properties over a wide tempera¬ture range of existence of the liquid state. Among the ionic liquids investigated, 1-alkyl- 3-methylimidazolium halides were found generally preferred for their low melting points and ease of handling and preparation.}, language = {en} } @techreport{SchmidtEfimova, author = {Schmidt, Peer and Efimova, Anastasia}, title = {Thermal Characterization of Ionic Liquids}, publisher = {NETZSCH-Ger{\"a}tebau GmbH}, address = {Selb}, pages = {14 -- 17}, abstract = {Ionic liquids (ILs) are currently of high interest due to their high performance physicochemical properties over a wide temperature range of existence of the liquid state. Among the ionic liquids investigated, 1-alkyl-3-methylimidazolium halides were found generally preferred for their low melting points and ease of handling and preparation.}, language = {en} } @misc{JurischkaDinterEfimovaetal., author = {Jurischka, Christoph and Dinter, Franziska and Efimova, Anastasia and Weiss, Romano and Schiebel, Juliane and Schulz, Christian and Fayziev, Bekzodjon and Schierack, Peter and Fischer, Thomas and R{\"o}diger, Stefan}, title = {An explorative study of polymers for 3D printing of bioanalytical test systems}, series = {Clinical Hemorheology and Microcirculation}, volume = {75}, journal = {Clinical Hemorheology and Microcirculation}, number = {1}, issn = {1875-8622}, doi = {10.3233/CH-190713}, pages = {57 -- 84}, abstract = {Background: The 3D printing is relevant as a manufacturing technology of functional models for forensic, pharmaceutical and bioanalytical applications such as drug delivery systems, sample preparation and point-of-care tests. Objective: Melting behavior and autofluorescence of materials are decisive for optimal printing and applicability of the product which are influenced by varying unknown additives. Methods: We have produced devices for bioanalytical applications from commercially available thermoplastic polymers using a melt-layer process. We characterized them by differential scanning calorimetry, fluorescence spectroscopy and functional assays (DNA capture assay, model for cell adhesion, bacterial adhesion and biofilm formation test). Results: From 14 tested colored, transparent and black materials we found only deep black acrylonitrile-butadiene-styrene (ABS) and some black polylactic acid (PLA) useable for fluorescence-based assays, with low autofluorescence only in the short-wave range of 300-400 nm. PLA was suitable for standard bioanalytical purposes due to a glass transition temperature of approximately 60°C, resistance to common laboratory chemicals and easy print processing. For temperature-critical methods, such as hybridization reactions up to 90°C, ABS was better suited. Conclusions: Autofluorescence was not a disadvantage per se but can also be used as a reference signal in assays. The rapid development of individual protocols for sample processing and analysis required the availability of a material with consistent quality over time. For fluorescence-based assays, the use of commercial standard materials did not seem to meet this requirement.}, language = {en} }